Alternating current motor



March 29, 1932. E, G. PARVlN 1,85L59'1 ALTERNATNG CURRENT MOTOR Filed June 2l. 1927 AMPEHES Patented Mar. 29, 1932 UNITED STATES PTENT OFFICE EDWARD G. PARWN, OF IROSELLE, NEW

JERSEY, ASSIGNOR TO ZOBELL ELECTRIC MOTOR CORPORATION, OF GARWOOD, NEW JERSEY, A CORPORATION OF NEW YORK ALTERNATING- CURRENT MOTOR Application filed June 21,

The present invention consists in an alternating current motor arrangement devised with the general object of insuring some or all of the following characteristics, namely:

- operat-ion at widely different speeds, and under widely different loads, a desirable and safe maximum no load speed, a motor torque which is practically at maximum at starting and which diminishes as the speed increases through the normal range, and all without objectionable sparking. Io this end I employ a simple shunt wound alternating current motor of the commutating type, and connect a resistance in series with the armature and held windings of the motor, which is adapted to materially increase the power factor of the motor field winding, while at the same time diminishing the power factor of the armature winding, and which increases the effective reaction between the armature and field windings.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, and the advantages possessed by it, reference should be had to the accompanying drawings and descriptive matter in which 3o I have illustrated and described a preferred embodiment of the invention.

In the drawings:

Fig. l is a diagrammatic representation of one embodiment of my invention;

Fig. 2 is a diagram illustrating power factor relations;

Fig. 3 is a diagram illustrating voltage and speed characteristics;

Fig. 4 is a diagram illustrating modifica- 4.0 tions of the motor arrangement shown in Fig. l; and

Fig. 5 is a diagram illustrating another modification.

In Fig. l, A represents a motor shown as a simple bipolar commutating motor having a field winding comprising a coil B on each motor pole, and an armature C with ordinary direct current windings connected in the usual manner to a commutator C', against diametrically opposed portions of which 1927. Serial No. 200,324.

brushes D bear. The field winding coils B are connected in series with one another between terminal conductors 3 and el. @ne of the brushes D is connected to the conduct-or 3 and the other brush is connected to the conductor 4, so that the armature and field windings are connected in parallel with one another between the conductors 8 and t. l and 2 represent supply conductors to which the conductors 3 and et may be respectively connected by a switch E. R represents a resistance in series with the armature and field windings. As shown, the resistance R is included in the conductor 4.

The eect on the power factor relations of a variation in the amount of resistance R in series with the armature and field windings of the motor shown in Fig. l, is illustrated in Fig. 2, wherein the armature, field and motor power factors at no load are represented by appropriately designated curves. In Fig. 2, abscissae measured along the line O-X represent different values of the resistance R, and ordinates measured along the line represent power factor percentages. It will be observed that as the value of the resistance R increases from zero through a small'range, there is a rapid and approximately proportional increase in the field power factor, and that as the value of the resistance R is increased through a further small range, the power factor continues to increase but at a diminishing rate, and that still further increases in the resistance R have practically no effect on the field power factor. As the resistance R increases from zero there is an initial rapid decrease in the power factors of the armature and of the motor as a whole, followed by more moderate decreases in these two power factors as the resistance is further increased through small ranges, and as the resistance is still further increased, there is practically no further change in the motor and armature power factors.

As illustrated in Fig. 2, the horizontal portion of the field power factor curve corresponds to a power factor of about 38%, and the horizontal portion of the motor power factor curve corresponds to a power factor that the value ot the of about 46%, but it will be understood that these percentages are given by way of illustration and not of limitation and that quite dii'erent percentages may be obtained with different motor arrangements and operating conditions'. Vlith the motor and the operating conditions to which the `power tact r diagram of Fig. 2 applies, I consider it desirable resistance employed should be approximately that indicated by the distance G-X- lilith that value, the difference between the armature and field power factors is but little above the minimum to which said difference can be reduced by further increases in the value ot the resistance 4lt, and the armature and iield reactions approach a maximum. The advantages of increasing the value of the resistance R beyond that representedby O-X under these circumstances are ordinarily not sufficient to compensate for the increased power consumption by the resistance It In Fig. 3 I have illustrated diagrammatically the variations in the line voltage, motor current, and no load motor speed or the motor to which the dia-gram 2 pertains, when the value ot the resistance R is varied and the line voltage is simultaneously varied to maintain a constant potential difference between the conductors 3 and 4. In Fig. 3 the different values of theV resistance R are represented by abscissae measured along the lines 0-X2, and tl e line voltage, motor current strength, and motor speeds are represented by ordinates measured along the line O-Yg.

While the new motor arrangement may be vused withadvantage under widely different conditions, it is of especial utility when used for opening and closing the doors of passenger cars and buildings. In such use, with a properly proportioned resistance R in series with the armature and iield windings ot the motor it is possible to make the motor torque a. practical maximum when the motor is started, and to make the motor torque diminish as the speed of the motor is increased to a maximum, and to limit the door closing speed to a sate maximum.

t will be understood, of course, that the invention is not limited to any such details oi the motor arrangement shown in Fig. l as the number of pairs of motor poles or brushes, and that in some cases either the iield or the armature winding, and particularly the latter, or botii, may have resistance connected in series with it which is not in series with the other winding: For example, as shown in il 4, a Vresistance It is connected in series with the armature in a portion of the motor circuit individual to the armature. The invention, however, requires that there must be a resistance, such as the resistance l, with which both the armature and the ield winding are in series. In such a use as that mentioned above for operating car doors, the motor must be reversible, and in Fig. 4 I have illustrated diagrammatically a two-pole double-throw reversing switch Ev for interchangeably connecting either motor brush to the conductor 3 while simultaneously connecting the other motor brush to theconductor 4.

In Fig. 5 I have illustrated a modification in which the two held coils B of a bipolar motor are connected in series with one another between the conductors 3 and 4, and a reversing switch E2 in connection with conductors 5, 6 and 7 forms a means for connecting the armature in shunt with either field coil. IV ith this arrangement when the switch E2 is in positionito connect the armature in shunt with one ot the field coils,lthe other ield'coil constitutes an impedance having comparatively little edect on the operation of the motor. As shown in Fig. 5, there Vis a. resistance R2 in the conductor 3, and-aresistance R3 in the conductor l, but it will be readily apparent that ii" the two resistances R2 and R3 were both located in the conductor 3 or lin the conducto-r l the operation of the arrangement shown in Fig. 5 would not be altered. V

`While in accordance with the provisions of lthe statutes, I have illustrated andy described the best form of embodiment of my invention now lrnown to me, it will be apparent to those skilled in the art that changes inay be made in the form of the apparatus'disclosed without departing from the spiritoi my invention as set forth in the appended claims, and that in some cases certain features ot my invention may be used to advantage without a corresponding use ot other features. Y

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

l. rlChe combination with a source of alternating current, or" a commutating motor having main armature and main'eld windings which in normal operation are connected in parallel with one another to said source, and a common resistance in series with each of said windings and said source.

2. A commutating alternating current motor, comprising main armature andV main iield windings which in normal operation-are connected in parallel with one another to the same source ot alternating current, and a common resistance in series with each of said windings and so proportioned as to make the ditterence between the no load power factors ot said windings relatively small.

3. A commutating alternating current moiin 

